FINAL DRAINAGE REPORT Road Improvements (MP 0.6)

FINAL DRAINAGE REPORT 17-03109 45.5 Road Improvements (MP 0.6) Prepared for: Prepared by: Mesa County Engineering Department 200 S. Spruce Street Grand Junction, CO 81501 DOWL 222 South Park Avenue Montrose, Colorado, 81401 (970) 249-6828 August 17, 2018

Final Drainage Report 31 Road Intersection Improvements TABLE OF CONTENTS 1. INTRODUCTION... 1 1.1 BACKGROUND... 1 1.2 PROJECT LOCATION... 1 FIGURE 1. 45.5 ROAD (MP 0.6) PROJECT AREA... 1 1.3 DESIGN CRITERIA... 2 1.4 PREVIOUS DESIGN INFORMATION... 2 1.3 TOPOGRAPHY... 3 1.4 VEGETATION... 3 1.5 GENERAL SOILS AND GEOLOGY... 3 1.6 EXISTING DRAINAGE FEATURES... 4 2. HYDROLOGIC ANALYSIS... 6 3. HYDRAULIC ANALYSIS.7 4. BANK STABILIZATION RECOMMENDATIONS... 9 5. CONCLUSIONS AND RECOMMENDATIONS...10 7. REFERENCES... 11 DOWL January 27, 2017 i

Final Drainage Report 31 Road Intersection Improvements Table 1: Table 2: Table 3: PFDS Rainfall Values for the Grand Valley Area Cover Conditions Hydrology Modeling Results LIST OF TABLES Figure 1: Figure 2: Figure 3. Figure 4. Figure 5. Figure 6. Figure 7. Figure 8. 45.5 Road (MP 0.6) Project Area Atwell Gulch Basin Map Photo of 45.5 Road at project location NRCS WSS Soil Map of Atwell Gulch Photo of RS 1110 showing erosion and temporary rip-rap HEC-RAS RS 1110 cross-section of existing conditions HEC-RAS RS 1110 cross-section with gabion wall Gabion Wall Schematic cross-section detail LIST OF FIGURES Appendix A: Appendix B: Appendix C: Appendix D: Existing and Proposed Project Site Plans NRCS Web Soil Survey Data NOAA 14 PFDS Data HEC-RAS Output Pre-Developed and Developed Conditions LIST OF APPENDICES DOWL January 27, 2017 ii

Final Drainage Report 45.5 Road (MP 0.6) Improvements 1. INTRODUCTION 1.1 Background As part of proposed roadway improvements at MP 0.6 on 45.4 Road in Mesa County, DOWL has prepared this Drainage Report for the region contributing runoff into the project area. Storm flows are currently conveyed by Atwell Gulch on the east side of 45.5 Road and they have eroded large portions of the roadway embankment at MP 0.6. This report is intended to present the following information: project site characteristics, identification of existing drainage system H & H components, drainage analysis and results, preliminary design for current project area improvements, conclusions and recommendations. 1.2 Project Location The 45.5 Road (MP0.6) Project (Project) is located approximately 0.6 miles north of the intersection of 45.5 Road and Colorado State Highway 330 north of Mesa, Colorado, within Mesa County. Refer to Exhibit 1 for the general project location. Figure 1. 45.5 Road (MP 0.6) Project Area DOWL March 15, 2018 1

Final Drainage Report 45.5 Road (MP 0.6) Improvements 1.3 Design Criteria The purpose of the project is to design improvements relating to erosion of the road prism on the west bank of Atwell Gulch at the MP 0.6 locations. Surface stormwater currently flows in in a meandering stream pattern that is eroding portions of 45.5 Road and endangering the asphalt pavement of the road. The Atwell Gulch drainage channels is well established on the east side of 45.5 Road and is directed towards the road in several sections as a cut bank. The scope of work for this drainage report is to determine and design bank stabilization that will accommodate the 100-year design storm in Atwell Gulch, an ephemeral stream channel. 1.4 Previous Design Information Per Mesa County, it does not appear that any existing drainage reports were prepared or are available for the 45.5 Road (MP0.6) project area. DOWL previously prepared drainage reports for Shire Gulch, the 45.5 Road Improvements Phases I/II and the 45.5 Road 4B projects. No known Atwell Gulch drainage reports were available as a reference for this report. Figure 2. Atwell Gulch basin upstream of the project location. DOWL March 15, 2018 2

Final Drainage Report 45.5 Road (MP 0.6) Improvements 1.3 Topography Topography of the project area for project area ranges from an elevation of approximately 7,923 feet (MSL) on the topographic highpoint to the east of the intersection, to 5,200 feet (MSL) at the low point of the project limits to the north and south. The general drainage direction of stormwater runoff is to the southwest at an average grade of approximately 413 feet per mile or 7.8%. 1.4 Vegetation Vegetation in the project area consists primarily of native grasses, shrubs. including rabbit brush and sagebrush and pinyon-juniper trees. Additionally, there are tamarisk trees adjacent to Atwell Gulch which are an invasive species and non-native to the project area. Figure 3. View looking west at vegetation adjacent to the project area. Eroded section of the 45.5 Road bank is to the lower left of the photo. 1.5 General Soils and Geology Information from the NRCS Web Soil Survey (WSS) site indicates that there are thirteen (13) mapped soil units identified in the Atwell Gulch basin. Table 1 below summarizes those soil DOWL March 15, 2018 3

Final Drainage Report 45.5 Road (MP 0.6) Improvements units. More detailed soils descriptions obtained from the WSS website are presented in Appendix B and in the geotechnical report prepared by DOWL for the project. In general, the project area and Atwell Gulch basin are composed of approximately 79% sandstone rock outcrops of the Ohio Creek member of the Mesa Verde formation and the remaining 21% represent colluvial loam soils derived from weathering of that rock. Slopes range from 3 percent up to 90 percent for vertical rock cliffs to the west and east of the MP 0.6 site. Figure 4. Project Soils Map. (Source: NRCS-USDA Web Soil Survey) 1.6 Existing Drainage Features As evidenced by the incised nature of the Atwell Gulch drainage channel on the east side of 45.5 Road, stormwater flows to the project area are readily conveyed towards the 45.5 Road section and then south towards Plateau Creek through numerous channels within the basin in addition to the main Atwell Gulch channel. Drainage features observed during our site visits include: access drive culverts on the west side of 45.5 Road, a 12-inch CMP culvert that DOWL March 15, 2018 4

Final Drainage Report 45.5 Road (MP 0.6) Improvements crosses 45.5 Road near Station 8+25 of the project plans and the 36-inch CMP culvert under SH 330 to the east of the 45.5 Road intersection. Figure 5. View looking downstream at right bank erosion adjacent to 45.5 road. Note sandstone bedrock at the surface of the stream channel and rip-rap placed along the bank and at the toe to minimize erosion of the bank. DOWL March 15, 2018 5

Final Drainage Report 45.5 Road (MP 0.6) Improvements 2. HYDROLOGIC ANALYSIS This section of the report reviews the sources for hydrologic data used hydraulic analysis in Section 4. In addition to the StreamStats data, which calculated the 100-year flow using the USGS regression equation for the northwest Hydrologic Region, we used the USDA Win TR 55 software and the CDWR Unit Hydrograph spreadsheet to estimate peak flow for the Shire Gulch basin. The recently published NOAA Atlas 14 was consulted for revisions to rainfall depth and frequency-duration for the interval storms over a 24-hour period. The data for Mesa, Colorado with a 90% confidence interval was used for our analysis and is presented in Appendix C. RETURN PERIOD 24-HR TOTAL PRECIPITATION (IN) 2-year 1.02 5-year 1.44 10-year 1.66 25-year 1.98 50-year 2.24 100-year 2.50 Table 1. Summary of NOAA Atlas 14 precipitation data for varying recurrence periods. RETURN PERIOD STREAMSTATS WIN TR-55 PEAK FLOWS (c.f.s) PEAK FLOWS (c.f.s.) 2-year 120 278 5-year 371 918 10-year 736 1350 25-year 1540 2062 50-year 2410 2684 100-year 3600 3353 Table 2. Summary of StreamStats Peak-Flow Statistics Data for Atwell Gulch Basin 2.1 Win TR 55 Model To confirm that StreamStats returned reasonable rainfall and flow data for the Atwell Gulch basin, we also modeled the basin using Win TR 55 software form the US Department of Agriculture (USDA). Output for this model is included in Appendix C of this report. Assumptions for the TR 55 model: Basin area = 6.92 sqare miles. This is slightly smaller than the area returned by the StreamStats program (8.04 sq. miles), but was calculated from USGS maps, and aerial photos using AutoCAD and appears to better represent the contributing basin for Atwell Gulch Weighted CN = 82 for arid rangeland, from StreamStats data Channel length = 6.58 miles Lc = 3.62 miles Slope = 0.078 ft/ft DOWL March 15, 2018 6

Final Drainage Report 45.5 Road (MP 0.6) Improvements NOAA Type A Design Storm The Win TR-55 calculation resulted in a peak flow at 3,353 cfs, which was similar to the StreamStats estimate of 3,600 cfs. To be conservative, the StreamStats values were used in HEC-RAS hydraulic analysis presented in Section 4 below. Win TR-55 output is presented in Appendix C of this report. 2.2 Existing 100-Year Floodplains\Easements There is no published FEMA floodplain insurance rate map (FIRM) for the Atwell Gulch drainage. A Flood Insurance Study (FIS) for Mesa County, FIS # 08029CV000A, completed in August 2010, does not include Atwell Gulch in the analysis. 3. HYDRAULIC ANALYSES In our preliminary options analysis, we proposed eight varying solutions to stabilizing the bank along 45.5 Road while avoiding construction below the ordinary highwater mark as mapped by ERO Resources. Mesa County selected a gabion wall option with spiral soil nails anchored by a 3-4-foot concrete to wall as shown in Figure 5 below. Using the information obtained in Section 3 as input into the US Army Corps of Engineers HEC-RAS 5.03 hydraulic modeling software, we calculated the minimum required gabion wall height and length pass the estimated 100-year flow of 3,600 cfs. The following assumptions were used for the HEC- RAS culvert sizing analysis: Maximum 100-year flow of 3,600 cfs obtained from StreamStats calculations. Cross-sections of the channel were taken from topographic survey performed by DOWL, as supplemented by digital terrain mapping (DTM) provided by Mesa County for the purpose of confirming gabion wall locations for the project. In order to simulate the bank stabilization proposed using the gabion walls and anchor nails, we modeled a bridge abutment in HEC-RAS. Both pre-developed and developed conditions models were created in HEC-RAS 5.03 to simulate flow conditions with and without the proposed gabion wall stabilization structure. The model output for both analyses are presented in Appendix D and summarized in Table 3 below. Analysis for scour was also performed in HEC-RAS and scour on river right segments will be managed with the bank stabilization structures described above. Scour analysis output is also presented in Appendix D. Condition 2-YR 5-YR 10-YR 25-YR 50-YR 100-YR Existing 5221.62 5223.75 5225.05 5227.80 5229.70 5231.91 Gabion Wall 5222.91 5223.95 5225.95 5227.90 5229.91 5232.15 Table 3. Summary of water surface elevations for pre-developed and developed conditions at RS 1085. DOWL March 15, 2018 7

Final Drainage Report 45.5 Road (MP 0.6) Improvements Figure 6. RS 1110 cross-section of existing conditions. 100-year W.S. elevation is 5231.91. Figure 7. RS 1110 cross-section of Option #2 gabion wall. Modeled as an abutment to a bridge to match structural conditions of design. 100-year water surface is at 5232.16. DOWL March 15, 2018 8

Final Drainage Report 45.5 Road (MP 0.6) Improvements 4. BANK STABILIZATION RECOMMENDATIONS After reviewing and presenting eight options for bank stabilization to Mesa County, Option #2 consisting of a gabion wall with soil anchors and a concrete retaining toe wall was selected for design and final modeling. This option is similar to past bank stabilization efforts by Mesa county along Atwell Gulch except for the retaining wall at the base and the anchors. Both of these additions should minimize future maintenance of this section. In sections of the project area that had slopes greater than 2H;1V, the DOWL design uses grouted and un-grouted rip-rap to retain the slope. In general, these areas are moderately well vegetated and appear stable under current flow conditions. The proposed gabion wall structure is reserved for those section of the channel that have eroded and are nearly vertical. The concrete toe wall will be doweled into underlying sandstone bedrock which is at or near the channel surface throughout the project area. The geotechnical report prepared By DOWL for the project explains the retaining structure in greater detail. Figure 8 below provides a typical gabion wall detail at RS 110 which was used in the hydraulic analyses in Section 3. Figure 8. Gabion Wall schematic design DOWL March 15, 2018 9

Final Drainage Report 45.5 Road (MP 0.6) Improvements 7. REFERENCES Mesa County Colorado GIS Website, http://gis.mesacounty.us/interactive.aspx. Mesa County Stormwater Management Manual (SWMM), dated December 31, 2007, issued April 2008. Natural Resources Conservation Service National Cooperative Soils Survey Website, http://websoilsurvey.nrcs.usda.gov/app/websoilsurvey.aspx. CDOT Standards and Specifications for Road and Bridge Construction (2017) Erosion Control and Stormwater Quality Field Guide, Colorado Department of Transportation (undated) DOWL March 15, 2018 11

APPENDIX A EXISTING AND PROPOSED SITE PLANS

EXISTING CONDITIONS ISSUED FOR BID R SC-VM-BA-45.5RD-ATWELL.dwg EXISTING CONDITIONS 45.5 ROAD IMPROVEMENTS MP 0.6 MESA COUNTY, CO

SITE PLAN ISSUED FOR BID R MC-CB-45.5 Road Design Base.dwg SITE PLAN 45.5 ROAD IMPROVEMENTS MP 0.6 MESA COUNTY, CO

APPENDIX B NRCS WEB SOIL SURVEY DATA

108 9' 27'' W Soil Map Douglas-Plateau Area, Colorado, Parts of Garfield and Mesa Counties; and Grand Mesa - West Elk... (GlobalWatershed) 108 4' 51'' W 4343000 4344000 4345000 4346000 4347000 4348000 4349000 4350000 4351000 746000 747000 748000 749000 750000 751000 39 16' 27'' N 39 16' 27'' N 4343000 4344000 4345000 4346000 4347000 4348000 4349000 4350000 4351000 39 11' 43'' N 39 11' 43'' N 746000 747000 748000 749000 750000 751000 752000 108 9' 27'' W N Map Scale: 1:42,600 if printed on A portrait (8.5" x 11") sheet. Meters 0 500 1000 2000 3000 Feet 0 2000 4000 8000 12000 Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 12N WGS84 108 4' 51'' W Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 1/26/2018 Page 1 of 3

Soil Map Douglas-Plateau Area, Colorado, Parts of Garfield and Mesa Counties; and Grand Mesa - West Elk Area, Colorado, Parts of Delta, Garfield, Gunnison, Mesa, and Montrose Counties (GlobalWatershed) MAP LEGEND MAP INFORMATION Area of Interest (AOI) Area of Interest (AOI) Soils Soil Map Unit Polygons Soil Map Unit Lines Soil Map Unit Points Special Point Features Blowout Borrow Pit Clay Spot Closed Depression Gravel Pit Gravelly Spot Landfill Lava Flow Marsh or swamp Mine or Quarry Miscellaneous Water Perennial Water Rock Outcrop Saline Spot Sandy Spot Severely Eroded Spot Sinkhole Slide or Slip Sodic Spot Spoil Area Stony Spot Very Stony Spot Wet Spot Other Special Line Features Water Features Streams and Canals Transportation Rails Interstate Highways US Routes Major Roads Local Roads Background Aerial Photography The soil surveys that comprise your AOI were mapped at 1:24,000. Please rely on the bar scale on each map sheet for map measurements. Source of Map: Natural Resources Conservation Service Web Soil Survey URL: Coordinate System: Web Mercator (EPSG:3857) Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area: Douglas-Plateau Area, Colorado, Parts of Garfield and Mesa Counties Survey Area Data: Version 10, Oct 12, 2017 Soil Survey Area: Grand Mesa - West Elk Area, Colorado, Parts of Delta, Garfield, Gunnison, Mesa, and Montrose Counties Survey Area Data: Version 7, Oct 10, 2017 Your area of interest (AOI) includes more than one soil survey area. These survey areas may have been mapped at different scales, with a different land use in mind, at different times, or at different levels of detail. This may result in map unit symbols, soil properties, and interpretations that do not completely agree across soil survey area boundaries. Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: 2, 2017 Dec 31, 2009 Mar The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident. Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 1/26/2018 Page 2 of 3

Soil Map Douglas-Plateau Area, Colorado, Parts of Garfield and Mesa Counties; and Grand Mesa - West Elk Area, Colorado, Parts of Delta, Garfield, Gunnison, Mesa, and Montrose Counties GlobalWatershed Map Unit Legend Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI 2 Badland 44.5 1.0% 3 Barx loam, 3 to 12 percent slopes 7 Biedsaw-Sunup gravelly loams, 10 to 40 percent slopes 12 Bunkwater very fine sandy loam, 1 to 8 percent slopes 32 Dominguez clay loam, 3 to 8 percent slopes 61 Rock outcrop-torriorthents complex, 15 to 90 percent slopes 66 Torriorthents, warm-rock outcrop complex, 35 to 90 percent slopes 69 Travessilla-Rock outcrop complex, 10 to 35 percent slopes 747.5 16.9% 25.5 0.6% 7.2 0.2% 56.1 1.3% 296.7 6.7% 1,204.1 27.2% 1,378.6 31.2% Subtotals for Soil Survey Area 3,760.2 85.0% Totals for Area of Interest 4,421.7 100.0% Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI 102 Badland 35.4 0.8% 103 Barx loam, 3 to 12 percent slopes 0.0 0.0% 180 Rock outcrop, shale 165.6 3.7% 192 Torriorthents, cool-rock outcrop, 35 to 90 percent slopes 193 Torriorthents, warm-rock outcrop, 35 to 90 percent slopes 391.7 8.9% 68.8 1.6% Subtotals for Soil Survey Area 661.5 15.0% Totals for Area of Interest 4,421.7 100.0% Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 1/26/2018 Page 3 of 3

APPENDIX C NOAA 14 PFDS DATA AND RUNOFF CALCULATIONS

StreamStats Page 2 of 3 StreamStats Report Region ID: CO Workspace ID: CO20180110181732926000 Clicked Point (Latitude, Longitude): 39.19627, -108.13989 Time: 2018-01-10 11:17:46-0700 Basin Characteristics Parameter Code Parameter Description Value Unit DRNAREA Area that drains to a point on a stream 8.04 square miles EL7500 Percent of area above 7500 ft 0 percent PRECIP Mean Annual Precipitation 15.33 inches BSLDEM10M Mean basin slope computed from 10 m DEM 25.5 percent CSL1085LFP Change in elevation divided by length between points 10 and 85 percent of distance along the longest flow path to the basin divide, LFP from 2D grid 159.3 feet per mi ELEV Mean Basin Elevation 5954 feet ELEVMAX Maximum basin elevation 7920 feet I24H100Y Maximum 24-hour precipitation that occurs on average once in 100 years 2.5 inches I24H2Y Maximum 24-hour precipitation that occurs on average once in 2 years - Equivalent to precitation intensity index 1.18 inches I6H100Y 6-hour precipitation that is expected to occur on average once in 100 years 1.87 inches I6H2Y Maximum 6-hour precipitation that occurs on average once in 2 years 0.79 LAT_OUT Latitude of Basin Outlet 4343255 degrees LC11BARE Percentage of barren from NLCD 2011 class 31 2.7 LC11CRPHAY Percentage of cultivated crops and hay, classes 81 and 82, from NLCD 2011 0 percent LC11DEV Percentage of developed (urban) land from NLCD 2011 classes 21-24 0 percent LC11FOREST Percentage of forest from NLCD 2011 classes 41-43 23.6 percent LC11GRASS Percent of area covered by grassland/herbaceous using 2011 NLCD 0 LC11IMP Average percentage of impervious area determined from NLCD 2011 impervious dataset 0.7 percent LC11SHRUB Percent of area covered by shrubland using 2011 NLCD 73.7 LC11SNOIC Percent snow and ice from NLCD 2011 class 12 0 LC11WATER Percent of open water, class 11, from NLCD 2011 0 LC11WETLND Percentage of wetlands, classes 90 and 95, from NLCD 2011 0 LFPLENGTH Length of longest flow path 7.79 miles LONG_OUT Longitude of Basin Outlet 228835 degrees MINBELEV Minimum basin elevation 5200 feet OUTLETELEV Elevation of the stream outlet in thousands of feet above NAVD88. 5200 feet RCN Runoff-curve number as defined by NRCS (http://policy.nrcs.usda.gov/opennonwebcontent.aspx?content=17758.wba) 82.54 RUNCO_CO Soil runoff coefficient as defined by Verdin and Gross (2017) 0.34 SSURGOA Percentage of area of Hydrologic Soil Type A from SSURGO 49 percent SSURGOB Percentage of area of Hydrologic Soil Type B from SSURGO 1.9 percent SSURGOC Percentage of area of Hydrologic Soil Type C from SSURGO 17.2 percent SSURGOD Percentage of area of Hydrologic Soil Type D from SSURGO 25 percent STATSCLAY Percentage of clay soils from STATSGO 25.22 percent STORNHD Percent storage (wetlands and waterbodies) determined from 1:24K NHD 0 percent https://streamstats.usgs.gov/ss/ 1/10/2018

StreamStats https://streamstats.usgs.gov/ss/ Page 3 of 3 1/10/2018 Parameter Code Parameter Description Value Unit TOC Time of concentration in hours 1.89 Peak-Flow Statistics Parameters [100 Percent (8.01 square miles) Northwest Region Peak Flow] Parameter Code Parameter Name Value Units Min Limit Max Limit DRNAREA Drainage Area 8.04 square miles 1 5250 EL7500 Percent above 7500 ft 0 percent 0 99 PRECIP Mean Annual Precipitation 15.33 inches 8 49 Peak-Flow Statistics Flow Report [100 Percent (8.01 square miles) Northwest Region Peak Flow] PIl: Prediction Interval-Lower, PIu: Prediction Interval-Upper, SEp: Standard Error of Prediction, SE: Standard Error (other -- see report) Statistic Value Unit SEp 2 Year Peak Flood 120 ft^3/s 113 5 Year Peak Flood 371 ft^3/s 88 10 Year Peak Flood 736 ft^3/s 79 25 Year Peak Flood 1540 ft^3/s 74 50 Year Peak Flood 2410 ft^3/s 74 100 Year Peak Flood 3600 ft^3/s 75 200 Year Peak Flood 5130 ft^3/s 76 500 Year Peak Flood 7740 ft^3/s 79 Peak-Flow Statistics Citations Capesius, J.P., and Stephens, V. C.,2009, Regional Regression Equations for Estimation of Natural Streamflow Statistics in Colorado: U. S. Geological Survey Scientific Investigations Report 2009-5136, 32 p. (http://pubs.usgs.gov/sir/2009/5136/http://pubs.usgs.gov/sir/2009/5136/)

Precipitation Frequency Data Server Page 1 of 4 NOAA Atlas 14, Volume 8, Version 2 MESA LAKES Station ID: 55-0622 Location name: Mesa, Colorado, USA* Latitude: 39.0583, Longitude: -108.0583 Elevation: Elevation (station metadata): 10000 ft** * source: ESRI Maps ** source: USGS POINT PRECIPITATION FREQUENCY ESTIMATES Sanja Perica, Deborah Martin, Sandra Pavlovic, Ishani Roy, Michael St. Laurent, Carl Trypaluk, Dale Unruh, Michael Yekta, Geoffery Bonnin NOAA, National Weather Service, Silver Spring, Maryland PF_tabular PF_graphical Maps_&_aerials Duration 5-min 10-min 15-min 30-min 60-min 2-hr 3-hr 6-hr 12-hr 24-hr 2-day 3-day 4-day 7-day 10-day 20-day 30-day 45-day 60-day PF tabular PDS-based point precipitation frequency estimates with 90% confidence intervals (in inches) 1 Average recurrence interval (years) 1 2 5 10 25 50 100 200 500 1000 0.129 (0.099-0.167) 0.188 (0.145-0.245) 0.230 (0.177-0.299) 0.317 (0.245-0.413) 0.446 (0.344-0.579) 0.574 (0.447-0.739) 0.691 (0.541-0.885) 0.917 (0.725-1.16) 1.17 (0.936-1.47) 1.49 (1.20-1.85) 1.89 (1.54-2.33) 2.19 (1.79-2.68) 2.45 (2.01-2.99) 3.18 (2.63-3.85) 3.81 (3.16-4.59) 5.46 (4.58-6.51) 6.80 (5.74-8.06) 8.50 (7.22-10.0) 9.96 (8.49-11.7) 0.205 (0.158-0.267) 0.300 (0.232-0.391) 0.366 (0.282-0.477) 0.482 (0.372-0.627) 0.614 (0.473-0.799) 0.746 (0.581-0.962) 0.850 (0.664-1.09) 1.06 (0.837-1.35) 1.33 (1.06-1.67) 1.68 (1.35-2.09) 2.15 (1.74-2.65) 2.51 (2.05-3.07) 2.82 (2.31-3.45) 3.66 (3.02-4.43) 4.35 (3.61-5.24) 6.15 (5.15-7.33) 7.64 (6.45-9.07) 9.61 (8.15-11.3) 11.3 (9.65-13.3) 0.323 (0.248-0.422) 0.474 (0.364-0.618) 0.577 (0.444-0.754) 0.740 (0.569-0.966) 0.883 (0.679-1.15) 1.03 (0.796-1.33) 1.11 (0.867-1.43) 1.31 (1.03-1.67) 1.60 (1.27-2.02) 2.02 (1.62-2.52) 2.59 (2.10-3.21) 3.05 (2.48-3.76) 3.45 (2.82-4.23) 4.45 (3.67-5.41) 5.24 (4.34-6.34) 7.28 (6.08-8.71) 9.02 (7.58-10.7) 11.4 (9.62-13.5) 13.5 (11.5-15.9) 0.415 (0.317-0.545) 0.607 (0.464-0.797) 0.741 (0.566-0.972) 0.943 (0.721-1.24) 1.10 (0.841-1.45) 1.26 (0.970-1.64) 1.33 (1.03-1.72) 1.52 (1.19-1.95) 1.85 (1.46-2.34) 2.32 (1.85-2.91) 2.98 (2.40-3.71) 3.53 (2.86-4.36) 4.00 (3.25-4.93) 5.13 (4.21-6.27) 6.01 (4.95-7.30) 8.23 (6.84-9.90) 10.2 (8.50-12.1) 12.8 (10.8-15.2) 15.2 (12.9-18.0) 0.531 (0.386-0.714) 0.777 (0.565-1.05) 0.948 (0.689-1.27) 1.21 (0.882-1.63) 1.39 (1.02-1.89) 1.57 (1.17-2.13) 1.64 (1.23-2.21) 1.84 (1.40-2.47) 2.21 (1.70-2.94) 2.76 (2.15-3.63) 3.54 (2.78-4.60) 4.21 (3.32-5.44) 4.78 (3.79-6.15) 6.10 (4.86-7.76) 7.08 (5.68-8.95) 9.55 (7.73-11.9) 11.7 (9.51-14.5) 14.7 (12.0-18.0) 17.5 (14.3-21.3) 0.613 (0.438-0.842) 0.897 (0.641-1.23) 1.09 (0.782-1.50) 1.40 (1.00-1.93) 1.61 (1.16-2.23) 1.81 (1.32-2.50) 1.88 (1.38-2.58) 2.09 (1.56-2.86) 2.50 (1.89-3.39) 3.12 (2.37-4.17) 3.99 (3.07-5.28) 4.76 (3.68-6.25) 5.41 (4.19-7.07) 6.87 (5.36-8.88) 7.93 (6.23-10.2) 10.6 (8.39-13.4) 12.9 (10.3-16.2) 16.1 (12.9-20.1) 19.1 (15.4-23.7) 0.688 (0.477-0.975) 1.01 (0.698-1.43) 1.23 (0.851-1.74) 1.58 (1.10-2.25) 1.82 (1.27-2.60) 2.05 (1.45-2.91) 2.13 (1.51-3.01) 2.36 (1.70-3.32) 2.82 (2.06-3.93) 3.50 (2.58-4.82) 4.47 (3.33-6.08) 5.33 (3.99-7.22) 6.06 (4.56-8.16) 7.66 (5.80-10.2) 8.80 (6.71-11.7) 11.6 (8.95-15.2) 14.1 (10.9-18.3) 17.5 (13.6-22.5) 20.7 (16.2-26.4) 1 Precipitation frequency (PF) estimates in this table are based on frequency analysis of partial duration series (PDS). 0.757 (0.505-1.11) 1.11 (0.739-1.63) 1.35 (0.901-1.98) 1.75 (1.17-2.59) 2.02 (1.36-2.99) 2.29 (1.56-3.37) 2.38 (1.63-3.48) 2.64 (1.83-3.84) 3.16 (2.22-4.55) 3.90 (2.77-5.56) 4.97 (3.56-6.99) 5.94 (4.29-8.30) 6.75 (4.89-9.39) 8.48 (6.19-11.7) 9.70 (7.13-13.3) 12.7 (9.43-17.1) 15.3 (11.4-20.5) 18.9 (14.2-25.1) 22.2 (16.7-29.3) 0.838 (0.539-1.28) 1.23 (0.789-1.87) 1.50 (0.962-2.28) 1.97 (1.27-3.01) 2.29 (1.48-3.51) 2.61 (1.71-3.97) 2.71 (1.79-4.11) 3.03 (2.03-4.56) 3.63 (2.46-5.41) 4.47 (3.06-6.59) 5.65 (3.91-8.22) 6.77 (4.72-9.78) 7.69 (5.38-11.1) 9.59 (6.77-13.6) 10.9 (7.75-15.4) 14.1 (10.1-19.7) 16.9 (12.2-23.3) 20.6 (15.0-28.3) 24.1 (17.6-32.8) 0.891 (0.565-1.40) 1.30 (0.827-2.05) 1.59 (1.01-2.50) 2.11 (1.34-3.32) 2.48 (1.57-3.89) 2.84 (1.82-4.42) 2.97 (1.92-4.59) 3.34 (2.18-5.10) 4.01 (2.65-6.06) 4.93 (3.29-7.36) 6.20 (4.18-9.16) 7.43 (5.04-10.9) 8.43 (5.76-12.3) 10.5 (7.21-15.1) 11.9 (8.22-17.1) 15.2 (10.7-21.7) 18.1 (12.8-25.5) 21.9 (15.6-30.7) 25.4 (18.2-35.5) Numbers in parenthesis are PF estimates at lower and upper bounds of the 90% confidence interval. The probability that precipitation frequency estimates (for a given duration and average recurrence interval) will be greater than the upper bound (or less than the lower bound) is 5%. Estimates at upper bounds are not checked against probable maximum precipitation (PMP) estimates and may be higher than currently valid PMP values. Please refer to NOAA Atlas 14 document for more information. Back to Top https://hdsc.nws.noaa.gov/hdsc/pfds/pfds_printpage.html?st=co&sta=55-0622&data=depth... 6/21/2018

Precipitation Frequency Data Server https://hdsc.nws.noaa.gov/hdsc/pfds/pfds_printpage.html?st=co&sta=55-0622&data=depth... Page 2 of 4 6/21/2018 PF graphical Back to Top

Precipitation Frequency Data Server https://hdsc.nws.noaa.gov/hdsc/pfds/pfds_printpage.html?st=co&sta=55-0622&data=depth... Page 3 of 4 6/21/2018 Maps & aerials Small scale terrain 3km + 2mi Large scale terrain 100km + 60mi Large scale map 100km + 60mi

Precipitation Frequency Data Server https://hdsc.nws.noaa.gov/hdsc/pfds/pfds_printpage.html?st=co&sta=55-0622&data=depth... Page 4 of 4 6/21/2018 100km + 60mi Back to Top US Department of Commerce National Oceanic and Atmospheric Administration National Weather Service National Water Center 1325 East West Highway Silver Spring, MD 20910 Questions?: HDSC.Questions@noaa.gov Disclaimer

APPENDIX D HEC-RAS MODEL OUTPUT

Plan: existing Ephemeral Wash Creek FL RS: 1110.08 Profile: 100-YR E.G. Elev (ft) 5234.85 Element Left OB Channel Right OB Vel Head (ft) 2.94 Wt. n-val. 0.040 W.S. Elev (ft) 5231.91 Reach Len. (ft) 25.00 25.00 25.00 Crit W.S. (ft) 5231.43 Flow Area (sq ft) 261.73 E.G. Slope (ft/ft) 0.013348 Area (sq ft) 261.73 Q Total (cfs) 3600.00 Flow (cfs) 3600.00 Top Width (ft) 37.49 Top Width (ft) 37.49 Vel Total (ft/s) 13.75 Avg. Vel. (ft/s) 13.75 Max Chl Dpth (ft) 9.53 Hydr. Depth (ft) 6.98 Conv. Total (cfs) 31159.8 Conv. (cfs) 31159.8 Length Wtd. (ft) 25.00 Wetted Per. (ft) 45.62 Min Ch El (ft) 5222.38 Shear (lb/sq ft) 4.78 Alpha 1.00 Stream Power (lb/ft s) 65.76 Frctn Loss (ft) 0.21 Cum Volume (acre-ft) 8.20 C & E Loss (ft) 0.41 Cum SA (acres) 1.39

45.5 Road - Existing conditions Plan: exist 6/21/2018 5240.04 Legend WS 500-YR WS 100-YR WS 50-YR WS 25-YR WS 10-YR Ground Bank Sta 5235 Elevation (ft) 5230 5225 5220 0 20 40 60 80 100 120 140 160 Station (ft)

HEC-RAS Plan: exist River: Ephemeral Wash Reach: Creek FL Reach River Sta Profile Q Total Min Ch El W.S. Elev Crit W.S. E.G. Elev E.G. Slope Vel Chnl Flow Area Top Width Froude # Chl (cfs) (ft) (ft) (ft) (ft) (ft/ft) (ft/s) (sq ft) (ft) Creek FL 1261.34 10-YR 736.00 5224.12 5228.79 5228.78 5230.29 0.018380 9.84 74.79 25.08 1.00 Creek FL 1261.34 25-YR 1540.00 5224.12 5231.28 5230.79 5232.95 0.012270 10.37 148.48 33.29 0.87 Creek FL 1261.34 50-YR 2410.00 5224.12 5233.10 5235.09 0.010834 11.31 213.01 37.13 0.83 Creek FL 1261.34 100-YR 3600.00 5224.12 5235.01 5237.41 0.010751 12.42 289.91 43.21 0.85 Creek FL 1261.34 500-YR 7740.00 5224.12 5240.54 5243.17 0.006623 13.32 639.82 73.94 0.70 Creek FL 1222.01 10-YR 736.00 5223.46 5229.28 5229.68 0.003733 5.11 144.13 40.38 0.48 Creek FL 1222.01 25-YR 1540.00 5223.46 5231.87 5232.37 0.003237 5.65 272.41 59.16 0.46 Creek FL 1222.01 50-YR 2410.00 5223.46 5233.92 5234.46 0.002772 5.86 411.01 75.56 0.44 Creek FL 1222.01 100-YR 3600.00 5223.46 5236.12 5236.68 0.002457 6.03 596.85 96.54 0.43 Creek FL 1222.01 500-YR 7740.00 5223.46 5241.94 5242.40 0.001722 5.40 1432.37 208.29 0.36 Creek FL 1191.23 10-YR 736.00 5223.24 5227.82 5227.82 5229.35 0.019135 9.91 74.28 24.69 1.01 Creek FL 1191.23 25-YR 1540.00 5223.24 5229.88 5229.88 5232.01 0.017467 11.72 131.41 31.23 1.01 Creek FL 1191.23 50-YR 2410.00 5223.24 5231.53 5231.53 5234.09 0.016463 12.83 187.88 37.23 1.01 Creek FL 1191.23 100-YR 3600.00 5223.24 5233.30 5233.30 5236.29 0.015725 13.87 259.52 44.20 1.01 Creek FL 1191.23 500-YR 7740.00 5223.24 5239.39 5242.07 0.009781 13.12 589.91 74.10 0.82 Creek FL 1166.23 10-YR 736.00 5223.01 5227.64 5228.59 0.010447 7.81 94.27 29.19 0.77 Creek FL 1166.23 25-YR 1540.00 5223.01 5229.71 5228.90 5231.15 0.010124 9.62 160.11 34.47 0.79 Creek FL 1166.23 50-YR 2410.00 5223.01 5231.26 5233.18 0.010756 11.13 216.58 38.65 0.83 Creek FL 1166.23 100-YR 3600.00 5223.01 5233.41 5235.53 0.009575 11.69 308.09 46.51 0.80 Creek FL 1166.23 500-YR 7740.00 5223.01 5239.51 5241.73 0.006489 11.96 646.95 66.92 0.68 Creek FL 1135 10-YR 736.00 5222.63 5226.64 5226.64 5228.11 0.018770 9.71 75.78 26.17 1.01 Creek FL 1135 25-YR 1540.00 5222.63 5228.60 5228.60 5230.68 0.017228 11.57 133.08 32.44 1.01 Creek FL 1135 50-YR 2410.00 5222.63 5230.45 5230.17 5232.77 0.013887 12.21 197.30 36.97 0.93 Creek FL 1135 100-YR 3600.00 5222.63 5232.88 5231.88 5235.20 0.010256 12.23 294.47 43.12 0.82 Creek FL 1135 500-YR 7740.00 5222.63 5238.97 5241.48 0.008385 12.71 609.05 70.07 0.76 Creek FL 1110.08 10-YR 736.00 5222.38 5225.95 5225.95 5227.44 0.018965 9.78 75.25 25.63 1.01 Creek FL 1110.08 25-YR 1540.00 5222.38 5227.90 5227.90 5230.13 0.017520 12.00 128.38 29.03 1.01 Creek FL 1110.08 50-YR 2410.00 5222.38 5229.70 5229.57 5232.36 0.015719 13.09 184.17 32.88 0.97 Creek FL 1110.08 100-YR 3600.00 5222.38 5231.91 5231.43 5234.85 0.013348 13.75 261.73 37.49 0.92 Creek FL 1110.08 500-YR 7740.00 5222.38 5238.93 5241.14 0.011583 11.92 649.40 110.55 0.87 Creek FL 1085.08 10-YR 736.00 5221.62 5225.84 5226.65 0.008625 7.22 101.93 30.48 0.70 Creek FL 1085.08 25-YR 1540.00 5221.62 5228.42 5229.47 0.006504 8.22 187.25 35.75 0.63 Creek FL 1085.08 50-YR 2410.00 5221.62 5230.42 5231.72 0.006139 9.17 262.81 39.86 0.63 Creek FL 1085.08 100-YR 3600.00 5221.62 5232.64 5234.23 0.005882 10.09 356.69 44.43 0.63 Creek FL 1085.08 500-YR 7740.00 5221.62 5239.14 5240.79 0.005047 10.32 749.75 80.02 0.59 Creek FL 1048.12 10-YR 736.00 5220.15 5224.50 5224.50 5226.12 0.018707 10.20 72.14 22.50 1.00 Creek FL 1048.12 25-YR 1540.00 5220.15 5226.66 5226.66 5228.97 0.017350 12.20 126.23 27.63 1.01 Creek FL 1048.12 50-YR 2410.00 5220.15 5228.74 5228.41 5231.27 0.014152 12.75 188.96 32.58 0.93 Creek FL 1048.12 100-YR 3600.00 5220.15 5231.12 5233.82 0.011742 13.18 273.10 38.43 0.87 Creek FL 1048.12 500-YR 7740.00 5220.15 5238.34 5240.52 0.006768 11.87 652.09 70.26 0.69 Creek FL 1010 10-YR 736.00 5219.32 5224.10 5225.22 0.011192 8.50 86.55 23.20 0.78 Creek FL 1010 25-YR 1540.00 5219.32 5226.58 5228.24 0.010581 10.33 149.03 27.11 0.78 Creek FL 1010 50-YR 2410.00 5219.32 5228.55 5230.69 0.010710 11.71 205.77 30.46 0.79 Creek FL 1010 100-YR 3600.00 5219.32 5230.73 5233.37 0.010779 13.03 276.25 34.22 0.81 Creek FL 1010 500-YR 7740.00 5219.32 5237.35 5240.17 0.009037 13.45 575.50 60.78 0.77 Creek FL 960 10-YR 736.00 5218.33 5223.73 5224.67 0.008915 7.79 94.49 24.14 0.69 Creek FL 960 25-YR 1540.00 5218.33 5226.29 5227.69 0.008627 9.46 162.83 29.15 0.71 Creek FL 960 50-YR 2410.00 5218.33 5228.34 5230.10 0.008595 10.64 226.43 33.17 0.72 Creek FL 960 100-YR 3600.00 5218.33 5230.61 5232.75 0.008429 11.73 306.93 37.63 0.72 Creek FL 960 500-YR 7740.00 5218.33 5237.40 5239.60 0.006506 11.89 651.19 64.81 0.66 Creek FL 913.91 10-YR 736.00 5218.21 5222.97 5224.17 0.012261 8.77 83.89 22.73 0.81 Creek FL 913.91 25-YR 1540.00 5218.21 5225.56 5227.21 0.010822 10.32 149.22 27.74 0.78 Creek FL 913.91 50-YR 2410.00 5218.21 5227.53 5229.62 0.010777 11.61 207.52 31.55 0.80 Creek FL 913.91 100-YR 3600.00 5218.21 5229.77 5232.28 0.010378 12.71 283.22 35.90 0.80 Creek FL 913.91 500-YR 7740.00 5218.21 5236.63 5239.25 0.006973 12.97 596.73 51.32 0.67 Creek FL 887.64 10-YR 736.00 5217.35 5223.29 5223.78 0.004053 5.64 130.47 32.23 0.49 Creek FL 887.64 25-YR 1540.00 5217.35 5226.12 5226.76 0.003511 6.42 239.87 42.60 0.48 Creek FL 887.64 50-YR 2410.00 5217.35 5228.29 5229.08 0.003301 7.12 338.26 48.12 0.47 Creek FL 887.64 100-YR 3600.00 5217.35 5230.73 5231.67 0.003109 7.76 464.09 55.02 0.47 Creek FL 887.64 500-YR 7740.00 5217.35 5237.54 5238.71 0.002427 8.69 890.20 66.00 0.42 Creek FL 851.5 10-YR 736.00 5216.83 5223.06 5223.61 0.004952 6.00 122.68 30.72 0.53 Creek FL 851.5 25-YR 1540.00 5216.83 5225.84 5226.61 0.004293 7.02 219.43 37.25 0.51 Creek FL 851.5 50-YR 2410.00 5216.83 5227.90 5228.92 0.004322 8.10 297.49 38.39 0.51 Creek FL 851.5 100-YR 3600.00 5216.83 5230.14 5231.49 0.004836 9.31 386.86 42.73 0.55

HEC-RAS Plan: exist River: Ephemeral Wash Reach: Creek FL (Continued) Reach River Sta Profile Q Total Min Ch El W.S. Elev Crit W.S. E.G. Elev E.G. Slope Vel Chnl Flow Area Top Width Froude # Chl (cfs) (ft) (ft) (ft) (ft) (ft/ft) (ft/s) (sq ft) (ft) Creek FL 851.5 500-YR 7740.00 5216.83 5237.22 5238.59 0.003566 9.37 825.86 70.65 0.48 Creek FL 826.5 10-YR 736.00 5216.38 5221.59 5221.59 5223.29 0.018846 10.43 70.55 20.88 1.00 Creek FL 826.5 25-YR 1540.00 5216.38 5223.87 5223.87 5226.25 0.017654 12.38 124.38 26.45 1.01 Creek FL 826.5 50-YR 2410.00 5216.38 5225.78 5225.78 5228.56 0.016650 13.38 180.18 32.64 1.00 Creek FL 826.5 100-YR 3600.00 5216.38 5228.65 5231.20 0.010958 12.80 281.35 37.46 0.82 Creek FL 826.5 500-YR 7740.00 5216.38 5235.81 5238.35 0.006727 12.79 605.18 48.97 0.64 Creek FL 816.14 10-YR 736.00 5213.53 5220.71 5220.71 5222.52 0.022898 10.78 68.26 19.36 1.01 Creek FL 816.14 25-YR 1540.00 5213.53 5223.43 5223.13 5225.67 0.017300 11.99 128.49 24.87 0.93 Creek FL 816.14 50-YR 2410.00 5213.53 5225.84 5228.23 0.013726 12.42 194.11 29.73 0.86 Creek FL 816.14 100-YR 3600.00 5213.53 5228.34 5231.05 0.012099 13.22 272.34 32.90 0.81 Creek FL 816.14 500-YR 7740.00 5213.53 5236.03 5238.15 0.007309 11.67 662.98 69.51 0.67 Creek FL 811.46 10-YR 736.00 5211.75 5220.79 5221.87 0.012030 8.35 88.10 20.72 0.71 Creek FL 811.46 25-YR 1540.00 5211.75 5223.98 5225.34 0.009311 9.34 164.81 27.27 0.67 Creek FL 811.46 50-YR 2410.00 5211.75 5226.30 5227.97 0.008776 10.36 232.62 30.76 0.66 Creek FL 811.46 100-YR 3600.00 5211.75 5228.73 5230.82 0.008851 11.58 310.83 33.65 0.67 Creek FL 811.46 500-YR 7740.00 5211.75 5236.16 5238.06 0.006475 11.06 700.12 70.19 0.62 Creek FL 795 10-YR 736.00 5212.70 5221.00 5221.61 0.004580 6.26 117.61 21.60 0.47 Creek FL 795 25-YR 1540.00 5212.70 5224.14 5225.11 0.005229 7.91 194.57 27.32 0.52 Creek FL 795 50-YR 2410.00 5212.70 5226.41 5227.75 0.005877 9.31 258.82 29.34 0.55 Creek FL 795 100-YR 3600.00 5212.70 5228.78 5230.62 0.006775 10.88 330.96 31.45 0.59 Creek FL 795 500-YR 7740.00 5212.70 5235.51 5230.69 5237.89 0.007779 12.37 625.47 56.76 0.66 Creek FL 775 10-YR 736.00 5212.75 5219.22 5219.22 5221.29 0.023180 11.53 63.81 15.62 1.01 Creek FL 775 25-YR 1540.00 5212.75 5222.07 5222.07 5224.75 0.020820 13.15 117.07 21.89 1.00 Creek FL 775 50-YR 2410.00 5212.75 5224.16 5224.16 5227.37 0.019766 14.38 167.57 26.35 1.01 Creek FL 775 100-YR 3600.00 5212.75 5226.30 5226.30 5230.20 0.019447 15.84 227.30 29.38 1.00 Creek FL 775 500-YR 7740.00 5212.75 5231.78 5231.78 5237.34 0.018842 18.92 409.12 36.81 1.00 Creek FL 747.74 10-YR 736.00 5212.45 5216.14 5216.05 5217.33 0.017278 8.78 83.84 32.66 0.97 Creek FL 747.74 25-YR 1540.00 5212.45 5218.25 5219.76 0.011545 9.85 156.35 36.18 0.84 Creek FL 747.74 50-YR 2410.00 5212.45 5219.96 5221.81 0.010360 10.90 221.19 39.65 0.81 Creek FL 747.74 100-YR 3600.00 5212.45 5221.80 5224.08 0.009962 12.10 297.58 43.41 0.81 Creek FL 747.74 500-YR 7740.00 5212.45 5226.00 5225.00 5229.87 0.011107 15.79 490.12 48.10 0.87 Creek FL 729.15 10-YR 736.00 5211.79 5216.32 5216.97 0.006965 6.47 113.76 34.81 0.63 Creek FL 729.15 25-YR 1540.00 5211.79 5218.44 5219.45 0.006506 8.05 191.36 38.29 0.63 Creek FL 729.15 50-YR 2410.00 5211.79 5220.16 5221.50 0.006600 9.28 259.63 41.10 0.65 Creek FL 729.15 100-YR 3600.00 5211.79 5222.01 5223.77 0.006958 10.65 338.17 44.12 0.68 Creek FL 729.15 500-YR 7740.00 5211.79 5226.34 5229.47 0.008810 14.19 545.38 52.65 0.78 Creek FL 700 10-YR 736.00 5211.47 5215.65 5216.67 0.012002 8.10 90.89 29.45 0.81 Creek FL 700 25-YR 1540.00 5211.47 5217.28 5217.04 5219.10 0.014727 10.82 142.35 33.85 0.93 Creek FL 700 50-YR 2410.00 5211.47 5219.05 5218.56 5221.16 0.012852 11.68 206.42 38.63 0.89 Creek FL 700 100-YR 3600.00 5211.47 5220.98 5220.28 5223.44 0.011706 12.58 286.14 43.70 0.87 Creek FL 700 500-YR 7740.00 5211.47 5225.94 5224.71 5229.19 0.009446 14.53 558.70 87.33 0.82 Creek FL 673.27 10-YR 736.00 5211.25 5215.78 5214.95 5216.27 0.006991 5.65 130.25 51.92 0.63 Creek FL 673.27 25-YR 1540.00 5211.25 5217.99 5218.51 0.004299 5.80 265.62 70.57 0.53 Creek FL 673.27 50-YR 2410.00 5211.25 5220.03 5220.54 0.002726 5.76 418.38 79.01 0.44 Creek FL 673.27 100-YR 3600.00 5211.25 5222.19 5222.75 0.002143 6.01 599.28 88.04 0.41 Creek FL 673.27 500-YR 7740.00 5211.25 5227.64 5228.35 0.001466 6.80 1192.40 131.47 0.36 Creek FL 658.5 10-YR 736.00 5211.07 5214.81 5214.81 5216.04 0.018198 8.93 82.46 33.32 1.00 Creek FL 658.5 25-YR 1540.00 5211.07 5217.00 5218.33 0.011002 9.26 166.36 43.12 0.83 Creek FL 658.5 50-YR 2410.00 5211.07 5219.26 5220.42 0.006826 8.64 279.02 55.94 0.68 Creek FL 658.5 100-YR 3600.00 5211.07 5221.48 5222.65 0.005067 8.67 415.16 65.13 0.61 Creek FL 658.5 500-YR 7740.00 5211.07 5226.76 5228.24 0.003743 9.77 792.38 77.82 0.54 Creek FL 630.31 10-YR 736.00 5209.67 5214.26 5215.34 0.012123 8.34 88.27 27.59 0.82 Creek FL 630.31 25-YR 1540.00 5209.67 5216.44 5217.99 0.011160 10.00 153.95 33.35 0.82 Creek FL 630.31 50-YR 2410.00 5209.67 5218.33 5220.12 0.010262 10.73 224.51 41.24 0.81 Creek FL 630.31 100-YR 3600.00 5209.67 5220.37 5222.37 0.009229 11.34 317.49 49.74 0.79 Creek FL 630.31 500-YR 7740.00 5209.67 5225.83 5228.03 0.006343 11.91 649.94 71.02 0.69 Creek FL 600 10-YR 736.00 5208.94 5213.93 5213.43 5214.96 0.011479 8.15 90.32 28.26 0.80 Creek FL 600 25-YR 1540.00 5208.94 5216.21 5215.31 5217.64 0.009704 9.60 160.37 33.24 0.77 Creek FL 600 50-YR 2410.00 5208.94 5218.08 5216.94 5219.80 0.009379 10.52 229.16 40.40 0.78 Creek FL 600 100-YR 3600.00 5208.94 5220.12 5218.78 5222.09 0.008758 11.26 319.73 48.38 0.77 Creek FL 600 500-YR 7740.00 5208.94 5225.56 5223.08 5227.82 0.006480 12.08 640.81 69.78 0.70 Creek FL 550 10-YR 736.00 5208.17 5212.62 5212.62 5214.18 0.018945 10.04 73.31 23.69 1.01 Creek FL 550 25-YR 1540.00 5208.17 5214.77 5214.72 5216.94 0.016906 11.81 130.38 29.52 0.99

HEC-RAS Plan: exist River: Ephemeral Wash Reach: Creek FL (Continued) Reach River Sta Profile Q Total Min Ch El W.S. Elev Crit W.S. E.G. Elev E.G. Slope Vel Chnl Flow Area Top Width Froude # Chl (cfs) (ft) (ft) (ft) (ft) (ft/ft) (ft/s) (sq ft) (ft) Creek FL 550 50-YR 2410.00 5208.17 5216.46 5216.46 5219.10 0.016443 13.05 184.72 35.00 1.00 Creek FL 550 100-YR 3600.00 5208.17 5218.26 5218.26 5221.40 0.015862 14.21 253.26 40.62 1.00 Creek FL 550 500-YR 7740.00 5208.17 5222.68 5222.68 5227.13 0.015156 16.92 457.34 51.79 1.00 Creek FL 500 10-YR 736.00 5207.28 5212.51 5213.36 0.008348 7.40 99.52 28.38 0.70 Creek FL 500 25-YR 1540.00 5207.28 5214.90 5216.10 0.007643 8.78 175.32 34.55 0.69 Creek FL 500 50-YR 2410.00 5207.28 5216.63 5218.22 0.008095 10.10 238.61 38.45 0.71 Creek FL 500 100-YR 3600.00 5207.28 5218.36 5220.48 0.009061 11.67 308.35 42.34 0.76 Creek FL 500 500-YR 7740.00 5207.28 5222.29 5221.46 5226.13 0.012063 15.72 492.30 51.26 0.89 Creek FL 450 10-YR 736.00 5206.22 5211.04 5211.04 5212.68 0.018728 10.27 71.67 22.18 1.01 Creek FL 450 25-YR 1540.00 5206.22 5213.27 5213.27 5215.45 0.017085 11.84 130.06 30.18 1.01 Creek FL 450 50-YR 2410.00 5206.22 5214.98 5214.98 5217.56 0.016065 12.90 186.87 36.35 1.00 Creek FL 450 100-YR 3600.00 5206.22 5216.74 5216.74 5219.80 0.015491 14.03 256.63 42.73 1.01 Creek FL 450 500-YR 7740.00 5206.22 5221.76 5220.99 5225.51 0.011672 15.53 498.49 53.49 0.90 Creek FL 400 10-YR 736.00 5205.86 5210.84 5211.71 0.008890 7.51 97.96 28.38 0.71 Creek FL 400 25-YR 1540.00 5205.86 5213.14 5214.37 0.008357 8.90 173.12 36.82 0.72 Creek FL 400 50-YR 2410.00 5205.86 5214.94 5216.44 0.008020 9.82 245.35 43.38 0.73 Creek FL 400 100-YR 3600.00 5205.86 5217.04 5218.77 0.007148 10.53 342.03 48.37 0.70 Creek FL 400 500-YR 7740.00 5205.86 5222.34 5224.66 0.006294 12.22 637.79 73.69 0.67 Creek FL 350 10-YR 736.00 5204.87 5210.45 5211.28 0.008012 7.27 101.22 28.39 0.68 Creek FL 350 25-YR 1540.00 5204.87 5212.88 5213.92 0.007453 8.19 187.93 41.94 0.68 Creek FL 350 50-YR 2410.00 5204.87 5214.77 5216.01 0.006320 8.91 270.37 45.07 0.64 Creek FL 350 100-YR 3600.00 5204.87 5216.90 5218.37 0.005776 9.73 369.85 48.56 0.62 Creek FL 350 500-YR 7740.00 5204.87 5222.31 5218.61 5224.29 0.004591 11.53 752.93 95.38 0.57 Creek FL 320.28 10-YR 736.00 5204.86 5209.79 5210.95 0.012290 8.64 85.22 24.89 0.82 Creek FL 320.28 25-YR 1540.00 5204.86 5212.08 5213.61 0.011225 9.90 155.54 33.93 0.82 Creek FL 320.28 50-YR 2410.00 5204.86 5213.65 5215.68 0.011592 11.44 210.62 36.47 0.84 Creek FL 320.28 100-YR 3600.00 5204.86 5215.34 5214.63 5218.01 0.012318 13.11 274.70 39.25 0.87 Creek FL 320.28 500-YR 7740.00 5204.86 5220.17 5220.17 5223.92 0.010593 15.77 546.31 89.68 0.83 Creek FL 292.35 10-YR 736.00 5204.34 5209.60 5210.58 0.010644 7.93 92.79 27.42 0.76 Creek FL 292.35 25-YR 1540.00 5204.34 5212.02 5213.23 0.009048 8.81 174.75 39.55 0.74 Creek FL 292.35 50-YR 2410.00 5204.34 5213.79 5215.24 0.008142 9.67 249.28 45.03 0.72 Creek FL 292.35 100-YR 3600.00 5204.34 5215.75 5217.46 0.007432 10.47 343.75 51.11 0.71 Creek FL 292.35 500-YR 7740.00 5204.34 5220.28 5222.74 0.006260 12.78 652.90 74.18 0.68 Creek FL 263.02 10-YR 736.00 5203.72 5208.72 5208.50 5210.15 0.016003 9.59 76.74 22.81 0.92 Creek FL 263.02 25-YR 1540.00 5203.72 5210.74 5210.74 5212.79 0.017631 11.47 134.30 33.42 1.01 Creek FL 263.02 50-YR 2410.00 5203.72 5212.29 5212.29 5214.81 0.016370 12.71 189.58 37.88 1.00 Creek FL 263.02 100-YR 3600.00 5203.72 5213.98 5213.98 5217.02 0.015573 13.98 257.46 42.60 1.00 Creek FL 263.02 500-YR 7740.00 5203.72 5218.42 5218.42 5222.35 0.011824 16.12 516.49 71.40 0.93 Creek FL 235.58 10-YR 736.00 5203.46 5208.58 5209.66 0.012583 8.35 88.10 28.22 0.83 Creek FL 235.58 25-YR 1540.00 5203.46 5210.19 5210.19 5211.98 0.017218 10.74 143.45 40.39 1.00 Creek FL 235.58 50-YR 2410.00 5203.46 5211.51 5211.51 5213.79 0.016077 12.12 198.93 43.82 1.00 Creek FL 235.58 100-YR 3600.00 5203.46 5213.00 5213.00 5215.82 0.015294 13.48 267.03 47.70 1.00 Creek FL 235.58 500-YR 7740.00 5203.46 5217.00 5217.00 5220.51 0.014039 15.04 514.96 74.46 1.01 Creek FL 200 10-YR 736.00 5202.94 5208.37 5209.18 0.009984 7.22 101.88 35.11 0.75 Creek FL 200 25-YR 1540.00 5202.94 5209.96 5211.17 0.013596 8.85 174.00 56.56 0.89 Creek FL 200 50-YR 2410.00 5202.94 5210.82 5210.77 5212.58 0.016242 10.66 226.12 63.58 1.00 Creek FL 200 100-YR 3600.00 5202.94 5211.98 5211.98 5214.16 0.015498 11.86 303.60 70.06 1.00 Creek FL 200 500-YR 7740.00 5202.94 5215.16 5215.16 5218.16 0.011567 14.00 580.73 106.08 0.93 Creek FL 175 10-YR 736.00 5202.67 5208.06 5208.92 0.011217 7.40 99.41 35.80 0.78 Creek FL 175 25-YR 1540.00 5202.67 5209.66 5209.40 5210.81 0.014285 8.60 179.06 63.31 0.90 Creek FL 175 50-YR 2410.00 5202.67 5210.54 5210.45 5212.14 0.015603 10.15 237.44 70.03 0.97 Creek FL 175 100-YR 3600.00 5202.67 5211.58 5211.58 5213.61 0.015920 11.43 314.83 79.02 1.01 Creek FL 175 500-YR 7740.00 5202.67 5214.39 5214.39 5217.01 0.013719 12.98 599.27 123.14 0.98 Creek FL 153.05 10-YR 736.00 5202.53 5208.01 5208.63 0.008855 6.27 117.36 46.36 0.69 Creek FL 153.05 25-YR 1540.00 5202.53 5209.74 5210.44 0.008225 6.72 229.22 78.67 0.69 Creek FL 153.05 50-YR 2410.00 5202.53 5210.79 5211.69 0.007942 7.60 317.13 88.22 0.71 Creek FL 153.05 100-YR 3600.00 5202.53 5211.72 5212.95 0.009534 8.92 403.68 101.58 0.79 Creek FL 153.05 500-YR 7740.00 5202.53 5213.51 5213.51 5216.00 0.014576 12.67 611.10 124.86 1.01 Creek FL 125 10-YR 736.00 5201.95 5207.07 5207.07 5208.22 0.019477 8.57 85.85 37.99 1.01 Creek FL 125 25-YR 1540.00 5201.95 5208.65 5208.65 5210.04 0.018071 9.47 162.69 59.71 1.01 Creek FL 125 50-YR 2410.00 5201.95 5209.83 5209.83 5211.31 0.017410 9.78 246.42 84.69 1.01 Creek FL 125 100-YR 3600.00 5201.95 5210.88 5210.88 5212.56 0.016233 10.39 346.46 103.63 1.00 Creek FL 125 500-YR 7740.00 5201.95 5213.21 5213.21 5215.42 0.014945 11.93 649.02 148.95 1.01

5240 45.5 Road - Gabion Option Plan: Option #2 - Run 1 6/21/2018 Gabion Wall.02 Legend WS 500-YR WS 100-YR WS 50-YR WS 25-YR WS 10-YR Ground Bank Sta 5235 Elevation (ft) 5230 5225 5220 0 20 40 60 80 100 120 140 160 Station (ft)

HEC-RAS Plan: gabion River: Ephemeral Wash Reach: Creek FL Reach River Sta Profile Q Total Min Ch El W.S. Elev Crit W.S. E.G. Elev E.G. Slope Vel Chnl Flow Area Top Width Froude # Chl (cfs) (ft) (ft) (ft) (ft) (ft/ft) (ft/s) (sq ft) (ft) Creek FL 1261.34 2-YR 120.00 5224.12 5225.89 5225.89 5226.56 0.003753 6.53 18.37 14.07 1.01 Creek FL 1261.34 5-YR 371.00 5224.12 5227.39 5227.39 5228.52 0.003225 8.51 43.60 19.66 1.01 Creek FL 1261.34 10-YR 736.00 5224.12 5228.78 5228.78 5230.29 0.002964 9.87 74.57 25.04 1.01 Creek FL 1261.34 25-YR 1540.00 5224.12 5230.79 5230.79 5232.89 0.002707 11.62 132.54 32.13 1.01 Creek FL 1261.34 50-YR 2410.00 5224.12 5232.37 5232.36 5234.97 0.002544 12.94 186.21 35.80 1.00 Creek FL 1261.34 100-YR 3600.00 5224.12 5234.36 5234.14 5237.29 0.002242 13.73 262.21 41.15 0.96 Creek FL 1222.01 2-YR 120.00 5223.46 5225.53 5225.82 0.001781 4.36 27.54 22.88 0.70 Creek FL 1222.01 5-YR 371.00 5223.46 5227.34 5227.70 0.000853 4.85 76.54 30.52 0.54 Creek FL 1222.01 10-YR 736.00 5223.46 5229.03 5229.49 0.000716 5.48 134.32 38.76 0.52 Creek FL 1222.01 25-YR 1540.00 5223.46 5231.66 5232.20 0.000582 5.93 259.91 57.39 0.49 Creek FL 1222.01 50-YR 2410.00 5223.46 5233.74 5234.31 0.000484 6.06 397.38 74.14 0.46 Creek FL 1222.01 100-YR 3600.00 5223.46 5235.96 5236.55 0.000416 6.19 581.47 94.36 0.44 Creek FL 1191.23 2-YR 120.00 5223.24 5225.09 5225.09 5225.71 0.003949 6.31 19.01 15.82 1.02 Creek FL 1191.23 5-YR 371.00 5223.24 5226.48 5226.48 5227.58 0.003333 8.42 44.08 20.33 1.01 Creek FL 1191.23 10-YR 736.00 5223.24 5227.82 5227.82 5229.35 0.003070 9.92 74.21 24.68 1.01 Creek FL 1191.23 25-YR 1540.00 5223.24 5229.88 5229.88 5232.01 0.002792 11.71 131.46 31.23 1.01 Creek FL 1191.23 50-YR 2410.00 5223.24 5231.53 5231.53 5234.09 0.002630 12.82 187.99 37.24 1.01 Creek FL 1191.23 100-YR 3600.00 5223.24 5233.30 5233.30 5236.29 0.002516 13.87 259.52 44.20 1.01 Creek FL 1166.23 2-YR 120.00 5223.01 5224.69 5224.69 5225.23 0.003919 5.89 20.36 19.22 1.01 Creek FL 1166.23 5-YR 371.00 5223.01 5225.87 5225.87 5226.85 0.003309 7.94 46.74 24.31 1.01 Creek FL 1166.23 10-YR 736.00 5223.01 5227.04 5227.04 5228.45 0.002988 9.53 77.19 27.66 1.01 Creek FL 1166.23 25-YR 1540.00 5223.01 5229.03 5228.90 5230.98 0.002503 11.22 137.20 32.74 0.97 Creek FL 1166.23 50-YR 2410.00 5223.01 5231.40 5233.23 0.001614 10.86 221.94 39.14 0.80 Creek FL 1166.23 100-YR 3600.00 5223.01 5233.99 5235.78 0.001220 10.72 335.84 48.29 0.72 Creek FL 1135 2-YR 120.00 5222.63 5224.22 5224.22 5224.76 0.003961 5.87 20.45 19.50 1.01 Creek FL 1135 5-YR 371.00 5222.63 5225.42 5225.42 5226.44 0.003290 8.09 45.86 22.80 1.01 Creek FL 1135 10-YR 736.00 5222.63 5226.64 5226.64 5228.11 0.003007 9.72 75.74 26.17 1.01 Creek FL 1135 25-YR 1540.00 5222.63 5229.27 5230.79 0.001777 9.91 155.33 34.08 0.82 Creek FL 1135 50-YR 2410.00 5222.63 5231.52 5233.11 0.001311 10.10 238.52 39.61 0.73 Creek FL 1135 100-YR 3600.00 5222.63 5234.02 5235.71 0.001055 10.43 345.22 45.18 0.67 Creek FL 1110.08 2-YR 120.00 5222.38 5224.01 5223.66 5224.28 0.001533 4.19 28.67 22.21 0.65 Creek FL 1110.08 5-YR 371.00 5222.38 5225.32 5224.78 5225.93 0.001556 6.24 59.48 24.53 0.71 Creek FL 1110.08 10-YR 736.00 5222.38 5226.78 5225.97 5227.67 0.001436 7.58 97.06 27.08 0.71 Creek FL 1110.08 25-YR 1540.00 5222.38 5229.47 5227.90 5230.65 0.001151 8.71 176.73 32.41 0.66 Creek FL 1110.08 50-YR 2410.00 5222.38 5231.60 5229.57 5233.04 0.001082 9.63 250.23 36.83 0.65 Creek FL 1110.08 100-YR 3600.00 5222.38 5233.99 5231.43 5235.69 0.001014 10.45 344.58 41.98 0.64 Creek FL 1110 Bridge Creek FL 1085.08 2-YR 120.00 5221.62 5222.91 5222.91 5223.38 0.003996 5.48 21.89 23.65 1.00 Creek FL 1085.08 5-YR 371.00 5221.62 5223.95 5223.95 5224.88 0.003364 7.72 48.04 26.40 1.01 Creek FL 1085.08 10-YR 736.00 5221.62 5225.05 5225.05 5226.42 0.003016 9.39 78.37 28.87 1.00 Creek FL 1085.08 25-YR 1540.00 5221.62 5227.80 5229.15 0.001474 9.29 165.71 34.50 0.75 Creek FL 1085.08 50-YR 2410.00 5221.62 5229.91 5231.44 0.001223 9.92 242.97 38.82 0.70 Creek FL 1085.08 100-YR 3600.00 5221.62 5232.15 5233.95 0.001117 10.74 335.16 43.43 0.68 Creek FL 1048.12 2-YR 120.00 5220.15 5221.75 5221.75 5222.36 0.003810 6.26 19.18 16.00 1.01 Creek FL 1048.12 5-YR 371.00 5220.15 5223.11 5223.11 5224.26 0.003273 8.58 43.23 19.23 1.01 Creek FL 1048.12 10-YR 736.00 5220.15 5224.49 5224.49 5226.12 0.003007 10.22 72.02 22.48 1.01 Creek FL 1048.12 25-YR 1540.00 5220.15 5226.66 5226.66 5228.97 0.002770 12.19 126.32 27.64 1.01 Creek FL 1048.12 50-YR 2410.00 5220.15 5228.41 5228.41 5231.25 0.002652 13.52 178.28 31.79 1.01 Creek FL 1048.12 100-YR 3600.00 5220.15 5230.33 5230.33 5233.72 0.002544 14.78 243.64 36.36 1.01 Creek FL 1010 2-YR 120.00 5219.32 5220.88 5220.88 5221.44 0.003885 5.99 20.02 18.14 1.01 Creek FL 1010 5-YR 371.00 5219.32 5222.13 5222.13 5223.24 0.003324 8.45 43.93 20.11 1.01 Creek FL 1010 10-YR 736.00 5219.32 5223.46 5223.46 5225.08 0.003043 10.22 72.02 22.20 1.00 Creek FL 1010 25-YR 1540.00 5219.32 5225.61 5225.61 5228.03 0.002870 12.49 123.34 25.57 1.00 Creek FL 1010 50-YR 2410.00 5219.32 5227.41 5227.41 5230.46 0.002792 14.00 172.09 28.52 1.01 Creek FL 1010 100-YR 3600.00 5219.32 5229.44 5229.44 5233.14 0.002716 15.42 233.41 31.96 1.01 Creek FL 960 2-YR 120.00 5218.33 5220.10 5220.10 5220.68 0.003971 6.14 19.55 17.16 1.01 Creek FL 960 5-YR 371.00 5218.33 5221.40 5221.40 5222.53 0.003363 8.51 43.57 19.66 1.01 Creek FL 960 10-YR 736.00 5218.33 5222.75 5222.75 5224.38 0.003102 10.25 71.82 22.25 1.01 Creek FL 960 25-YR 1540.00 5218.33 5224.91 5224.91 5227.29 0.002893 12.37 124.47 26.42 1.00 Creek FL 960 50-YR 2410.00 5218.33 5226.72 5226.72 5229.65 0.002762 13.75 175.30 29.98 1.00 Creek FL 960 100-YR 3600.00 5218.33 5228.68 5228.68 5232.24 0.002684 15.13 237.90 33.84 1.01 Creek FL 913.91 2-YR 120.00 5218.21 5219.76 5219.76 5220.33 0.003876 6.08 19.74 17.24 1.00 Creek FL 913.91 5-YR 371.00 5218.21 5221.05 5221.05 5222.19 0.003356 8.53 43.48 19.44 1.01 Creek FL 913.91 10-YR 736.00 5218.21 5222.40 5222.40 5224.06 0.003126 10.33 71.25 21.74 1.01 Creek FL 913.91 25-YR 1540.00 5218.21 5224.61 5224.60 5227.02 0.002906 12.45 123.66 25.90 1.00